Makes sense the needle jumping because you are throwing variable power (V x A) from the head depending on how hard you play and etc. The RMS power is different so the audio voltage is also different, and using it backwards you probably are 'tilting' the VU meter you're hitting it backwards with oscilating voltage...rgalpin wrote:regarding the idea of IN vs OUT when you say you are running it backwards... my thinking is that:
NORMAL USAGE:
in normal usage: wall voltage goes IN thru the plug that you plug into the wall (MALE)
>> VARIAC reduces voltage >>
reduced voltage comes OUT of the FEMALE receptacle on the variac
with that thinking i go:
AMP TO CAB USAGE:
AMP SPKR OUT >> MALE variac plug >>[variac @ 60V] >> FEMALE receptacle on variac >> speaker cab
when i do this, i see the variac needle jumping when i play.
is this the same as what you do jnew?
I love the name of this thread!! awesome.
Regarding the impedance matching, I've read a couple of articles saying that there's no such thing... output impedance WILL vary a LOT also, and it is incredibly lower than the usual 4, 8, 16ohm that we see on the amp and speakers... not sure if that's true but using the variac LOWER than the 90V (15ohm reading dc resistance) tends to increase the impedance, isn't that right? Jnew did you try measuring your 2nd variac's output when the dimer is lower than 90v to see what happends?